1. Technical Field
This invention relates to novel organosilicon compounds which are added to various thermosetting elastomer compositions as adhesive aids.
2. Background Art
Known adhesive aids added to conventional thermosetting elastomer compositions include those having alkoxysilyl groups, acid anhydride groups and SiH groups. Although some adhesive aids achieve good adherence, there is a desire to have compounds more effective as adhesive aids.
It has been found that organosilicon compounds having in a molecule (A) a perfluoroalkyl group of at least 3 carbon atoms which may be separated by an etheric oxygen atom, (B) a monovalent hydrocarbon group containing a carboxylic acid anhydride structure, and (C) a hydrosilyl group are effective as adhesive aids, especially as adhesive aids in elastomer compositions containing fluorinated compounds for enhancing their adhesion to metals.
The organosilicon compound of the invention has in a molecule (A) a perfluoroalkyl group of at least 3 carbon atoms which may be separated by an etheric oxygen atom, (B) a monovalent hydrocarbon group containing a carboxylic acid anhydride structure, and (C) a hydrosilyl (SiH) group.
Specifically, the organosilicon compound has the average compositional formula (1) and preferably the general formula (2), (3) or (4).
xe2x80x83RfaR1bR2cHdSiO(4xe2x88x92axe2x88x92bxe2x88x92cxe2x88x92d)/2xe2x80x83xe2x80x83(1)
In formula (1), Rf is a monovalent organic group containing a perfluoroalkyl group of at least 3 carbon atoms which may be separated by an etheric oxygen atom,
R1 is a substituted or unsubstituted monovalent hydrocarbon group,
R2 is a monovalent hydrocarbon group containing a carboxylic acid anhydride structure,
a, b, c and d are numbers satisfying:
0.01xe2x89xa6axe2x89xa650.5, preferably 0.05xe2x89xa6axe2x89xa60.3,
0xe2x89xa6bxe2x89xa62, preferably 0.5xe2x89xa6bxe2x89xa61.5,
0.01xe2x89xa6cxe2x89xa60.5, preferably 0.05xe2x89xa6cxe2x89xa60.3,
0.01xe2x89xa6dxe2x89xa60.5, preferably 0.05xe2x89xa6dxe2x89xa60.3, and
2xe2x89xa6a+b+c+dxe2x89xa63. 
In formula (2), R3 is a substituted or unsubstituted divalent hydrocarbon group,
R4 and R5 each are a substituted or unsubstituted monovalent hydrocarbon group,
R6 is independently hydrogen, Rf, R1 or R2, wherein Rf, R1 and R2 are as defined above, at least one hydrogen, at least one Rf and at least one R2 are contained in a molecule, and
e is an integer of 0 or 1. 
In formula (3), R4 is a substituted or unsubstituted monovalent hydrocarbon group; R6 is independently hydrogen, Rf, R1 or R2, wherein Rf, R1 and R2 are as defined above; at least one hydrogen, at least one Rf and at least one R2 are contained in a molecule; and m is a positive integer of at least 3 and preferably 3 to 8. 
In formula (4), R4 is a substituted or unsubstituted monovalent hydrocarbon group; R6 is independently hydrogen, Rf, R1 or R2, wherein Rf, R1 and R2 are as defined above; at least one hydrogen, at least one Rf and at least one R2 are contained in a molecule; n is a positive integer of at least 1, preferably 1 to 500 and more preferably 5 to 200; and R7 is R4 or a group of the following formula (5): 
wherein R4 and R6 are as defined above.
More illustratively, the substituted or unsubstituted monovalent hydrocarbon groups represented by R1, R4 and R5 are preferably those of 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, for example, alkyl groups such as methyl, ethyl and propyl, cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl and tolyl, and the foregoing groups in which some hydrogen atoms are substituted with halogen atoms.
The monovalent hydrocarbon group containing a carboxylic acid anhydride structure, represented by R2, is not critical as long has it has a carboxylic acid anhydride structure. Groups of the following formula are preferred. 
Herein R7 is a divalent hydrocarbon group having 1 to 15 carbon atoms, and especially 2 to 10 carbon atoms, for example, an alkylene or alkenylene group.
Illustrative examples are given below. 
The substituted or unsubstituted divalent hydrocarbon groups represented by R3 are preferably those of 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, for example, alkylene groups such as methylene, ethylene and propylene, cycloalkylene groups such as cyclohexylene, arylene groups such as phenylene, and the foregoing groups in which some hydrogen atoms are substituted with halogen atoms.
The monovalent organic groups containing a perfluoroalkyl group of at least 3 carbon atoms which may be separated by an etheric oxygen atom, represented by Rf, include
F(CxF2x)CH2CH2xe2x80x94,
F(CxF2x)CH2CH2CH2xe2x80x94, and
F(CyF2yO)pCzF2zxe2x80x94Axe2x80x94,
wherein x is 3 to 20, y is 1 to 4, z is 1 to 10, p is 1 to 100, y multiplied by p is at least 2, and A is a divalent organic group, for example, an alkylene group such as methylene, ethylene or propylene.
Illustrative, non-limiting examples of the organic groups represented by Rf are given below. Note that Me is methyl.
C4F9CH2CHxe2x80x94
C8F17CH2CH2CH2xe2x80x94
C3F7O(CF2CF2CF2O) hCF2CF2CH2CH2xe2x80x94(e.g., h=1 to 50)
Fxe2x80x94(CF2O)h(CF2CF2O) iCF2CH2CH2xe2x80x94(e.g., h=1 to 50, i=1 to 50)
Illustrative examples of the organosilicon compounds according to the invention are given below. They are typical examples, and the inventive compounds are not limited thereto. Note that Me is methyl. 
The organosilicon compounds of the invention can be synthesized, for example, by the following method. The starting compound is an organosilicon compound having fluorine-modified groups, represented by the formula:
RfaR1bHdSiO(4xe2x88x92axe2x88x92bxe2x88x92d)/2
wherein Rf and R1 are as defined above, and 0.01xe2x89xa6axe2x89xa60.5, 0xe2x89xa6bxe2x89xa62, 0.01xe2x89xa6dxe2x89xa60.5, and 2xe2x89xa6a+b+dxe2x89xa63. By effecting addition or hydrosilylation reaction of an acid anhydride having an ethylenically unsaturated group to the organosilicon compound having fluorine-modified groups in the presence of a hydrosilylation catalyst such as a platinum complex compound, the end compound is obtainable.
The reaction temperature is usually about 50 to 150xc2x0 C., preferably about 70 to 120xc2x0 C. If necessary, the reactants are diluted with a solvent such as toluene, xylene or 1,3-bistrifluoromethylbenzene.
Most often, the organosilicon compounds of the invention are added to thermosetting elastomer compositions as adhesion aids whereby the compositions are improved in adhesion to various materials including metals and alloys such as aluminum, iron, stainless steel, nickel alloys, chromium alloys and copper alloys, plastics such as acrylic resins, nylon, PPS, PBT, PET, epoxy resins, polyimides and polyvinyl chloride, and ceramics such as alumina and silicon nitride.